In recent years, secondary batteries are used for various purposes including electric vehicles. The secondary batteries are included in a device (hereinafter referred to as power storage device), such as an electric vehicle, and the power storage device is connected to a charge/discharge device to be charged or discharged.
In the case where the charge/discharge device is not an authentic one but an unauthorized one, the unauthorized device could develop performance problems, burst into flame, cause electric leakage, and could be misused for theft of electricity. Moreover, when the unauthorized charge/discharge device and a power storage device are connected with each other, information may be exchanged therebetween, which could cause information leakage. In relation to the above problems, some techniques have been proposed to prevent connections to unauthorized devices (see Patent Literatures 1 to 3, for example).